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Abstract: The first three hyper-velocity stars HVS unbound to the Galaxy wereserendipitously discovered in 2005. The only suggested origin of hyper-velocitystars is the Galactic Centre as it hosts a super-massive black hole capable ofaccelerating stars to such high velocities. Only one HVS, the sdO star US 708,is known to be an old low mass star, while HE 0437$-$5439 is an apparentlynormal early-type B-star, too short-lived to originate from the GalacticCentre, but could possibly come from the LMC. A systematic survey has led tothe discovery of seven new HVS of late B-type similar to the prototype HVS1,which can either be massive stars 3 Msun or horizontal branch stars,sufficiently long-lived to have travelled from the Galactic Centre. We presentnew spectral analyses of five known HVS as well as of a newly discoveredcandidate. It is possible that the late B-type HVS are a mix of main sequenceand evolved BHB stars. In view of the time scale problem we revisit HE0437$-$5439 and discuss a possible subluminous nature of this star.



Autor: Uli Heber, Heiko Hirsch, Heinz Edelmann, Ralf Napiwotzki, Simon O`Toole, Warren Brown, Martin Altmann

Fuente: https://arxiv.org/







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